Magnetically levitated space elevator to low-earth orbit (2001) [pdf]

How is the elevator car in a space elevator accelerated horizontally? That's what reaching orbit is, right? Horizontal acceleration?

The car starts out on the ground at 465m/s. It has to accelerate to 11,068 km/h.

What makes it accelerate? The cable, without any force applied to it anywhere? Or is there a rocket on that car?

To put mass into orbit, you have to accelerate that mass. And do it without decelerating the elevator.

There are no free lunches.

Or, you know, use a rocket...? I dont see an issue with Hydrogen Oxygen rocket propellants at all.

One thing with a space elevator that makes it so much more efficient than rockets is precisely because you don't necessarily need the payload itself to supply this horizontal acceleration. The space elevator is attached to the ground at one end, and the other is way up in orbit. There must be forces in play _already_ for the entire thing to stay standing, before you get to any concept of a payload/car. Part of the idea of building the elevator in the first place is to solve for these orbital forces in a generalized way independent of the payloads themselves. It's like strapping various sized rockets to your various specific payloads, versus building a generalized model of a rocket ship, and then just putting the various payloads inside the generalized rocket ship. Space elevator is a further evolution of the concept. You don't even need to use the rocket ship abstraction anymore. You're generalizing/abstracting the orbital transition itself into the structure of the elevator, and then just send things up and down it. The payload now only needs to worry about moving along the elevator, the elevator itself has already "solved" for the orbital horizontal acceleration by nature of its structure existing in the first place.

In terms specifically of mass/energy conservation, as the other reply said, energy is borrowed from either the earth's rotation and/or kinetic energy from a counterweight at the end of the elevator up in orbit.

Several prompts later …

The gap between current material science and the required advancements for constructing a magnetically levitated space elevator is significant. Let's break down the key areas where advancements are needed and assess the current state compared to the required state:

1. Superconducting Materials Current State:

NbTi Superconductors: NbTi (Niobium-Titanium) superconductors are among the most common, with critical temperatures around 9-10 K. They are widely used in MRI machines and particle accelerators. NbTi can sustain high current densities and generate substantial magnetic fields, but only at very low temperatures maintained by complex and costly cryogenic systems. Required State:

Higher Temperature Superconductors: For a space elevator, superconductors that can operate at higher temperatures would reduce the need for extensive cryogenic cooling, thus making the system more practical and less costly. Currently, high-temperature superconductors (HTS) exist (like YBCO - Yttrium Barium Copper Oxide), which can operate above 77 K (the boiling point of liquid nitrogen), but they are not yet produced in long, high-quality, and affordable lengths suitable for large-scale engineering projects. Gap Analysis:

The primary challenge is to develop superconductors that can operate at higher temperatures with sufficient current densities and stability. The current material science has not yet achieved a commercially viable production of long-length HTS with consistent quality and performance required for such applications. 2. Carbon Nanotubes and Advanced Fibers Current State:

Carbon Nanotubes (CNTs): CNTs are known for their extraordinary tensile strength and low density, making them ideal candidates for space elevator cables. However, the production of long, defect-free CNTs with consistent properties remains a significant challenge. Current production techniques yield short lengths with varying qualities, and scaling up these methods while maintaining material integrity is difficult. Required State:

Mass Production of High-Quality CNTs: For a space elevator, extremely long CNTs or similarly strong materials are required to construct a cable that can withstand the enormous stresses involved. These materials must be lightweight yet possess ultra-high tensile strength and stability over long periods. Gap Analysis:

The major hurdle is the ability to produce continuous lengths of high-quality CNTs or alternative advanced fibers at a commercial scale. The technology for producing and manipulating these materials at the necessary scale is still in its infancy. 3. Structural Materials and Stability Current State:

Composite Materials: Current composite materials, including carbon fiber composites, offer high strength-to-weight ratios. However, they are not yet capable of withstanding the specific stress and environmental conditions required for a space elevator, particularly in terms of radiation resistance and thermal stability. Required State:

Advanced Composites and Alloys: Materials need to be developed that can endure the harsh conditions of space, including temperature extremes, radiation, and micrometeorite impacts, while maintaining structural integrity over potentially very long periods. Gap Analysis:

Development is needed in creating materials that not only provide the necessary strength and durability but also can be manufactured and maintained at a reasonable cost. Improvements in radiation shielding and thermal management materials are also required. 4. Cooling and Power Systems Current State:

Cryogenic Cooling: Current cryogenic systems can maintain superconductors at low temperatures, but they are heavy, complex, and energy-intensive. They are impractical for continuous, large-scale applications like a space elevator. Required State:

Efficient Cooling Solutions: More efficient and lightweight cooling systems are required to maintain superconductors at operational temperatures without prohibitive power consumption. Alternatively, development of superconductors that operate at higher temperatures, requiring less intensive cooling, would be beneficial. Gap Analysis:

Significant innovation is needed in both cooling technology and power systems to make a space elevator feasible. The challenge is to achieve efficient, reliable, and cost-effective solutions that can be integrated into the elevator structure. Summary The gap between current capabilities and the required advancements is substantial. While we have foundational materials and technologies, such as NbTi superconductors and carbon nanotubes, they are not yet developed to the extent necessary for practical use in a space elevator. Advances in high-temperature superconductors, scalable production of high-quality carbon nanotubes, and the development of lightweight yet strong structural materials are critical.

Material science must progress significantly in these areas to move closer to realizing the concept of a magnetically levitated space elevator. This will require substantial research, development, and potentially novel breakthroughs in materials engineering and related technologies. The timeline for achieving these advancements is uncertain, and it could span several decades.